Identification and Analysis of Multiple Glycine Transport Systems in Isolated Mammalian Renal Tubules

Abstract

Abstract Rabbit renal tubule segments, prepared by collagenase digestion, were used to study glycine transport. A distinct two-limbed curve found when studying the effects of substrate concentration on transport indicated the presence of at least two transport systems for glycine. These systems could not be distinguished by their response to metabolic inhibitors or the removal of sodium from the incubation medium. Proline and alanine both inhibited glycine competitively, but were shown to share different transport systems with glycine. The use of alanine and proline at maximal inhibitory concentrations allowed the separation of glycine transport into three kinetically distinct systems. The kinetic constants derived from this analysis were examined with the aid of a computer program and the computed values were found to agree with the experimental determinations.